Test of a 2 MVA medium voltage HTS fault current limiter module made of YBCO coated conductors

A fault current limiter module for medium voltage applications has been built and tested successfully. The module corresponds to one phase of a 3-phase limiter for the 13 kV-class distribution voltage level. The resistive type limiter consists of 15 bifilar coils wound from a total of 15 x 50 m of AMSC's 344S superconductors, a commercially available second generation YBCO tape stabilized by stainless steel laminates. The module has a rated current of 300 Arms and a rated voltage of 7.5 kV corresponding to a nominal apparent power of 2.25 MVA. The cryostat is equipped with commercial current feed-throughs and the module is operated in liquid nitrogen at atmospheric pressure. For long term operation as a closed system a commercial cryogenic refrigerator coldhead is installed. Power tests and dielectric tests of the module have been performed at the IPH Berlin (Institut "Pruffeld fur elektrische Hochleistungstechnik") up to prospective currents of 28 kA. In standard power tests at voltages up to 7.8 kV and fault hold times of about 50 ms an excellent limiting performance was observed both at various prospective fault currents and at different fault starting phase angles. Within a second experimental series, an appropriate shunt reactor was connected in parallel to the limiter. The benefit of this method is that the limited current can be adjusted to the customers needs and the required amount of HTS-wire can be also appreciably reduced. The setup of the module and the test results are reported.